The word “printer” as used herein encompasses any apparatus, such as a digital copier, book marking machine, facsimile machine, multi-function machine, etc., that produces an image with a colorant on recording media for any purpose. Inkjet printers have one or more printheads that eject drops of liquid ink from inkjet ejectors to form the image on the surface of an image receiving surface. Full color inkjet printers typically use a plurality of ink reservoirs to store a number of differently colored inks for printing. A commonly known full color printer has four ink reservoirs. Each reservoir stores a different color ink, namely, cyan, magenta, yellow, and black ink, for the generation of full color images.
By way of example, FIG. 8 depicts a prior art continuous web inkjet printer 800. In the embodiment shown, the printer 800 implements a process for printing onto a continuous media web. The continuous web printer system 800 includes twenty print modules 880-899, a controller 828, a memory 829, guide roller 815, guide rollers 816, pre-heater roller 818, apex roller 820, leveler roller 822, tension sensors 852A-852B, 854A-854B, and 856A-856B, and velocity sensors, such as encoders 860, 862, and 864. The print modules 880-899 are positioned sequentially along a media path P and form a print zone from a first print module 880 to a last print module 899 for forming images on a print medium 814 as the print medium 814 travels past the print modules. Each print module 880-883 provides a magenta ink. Each print module 884-887 provides cyan ink. Each print module 888-891 provides yellow ink. Each print module 892-895 provides black ink. Each print module 896-899 provides a clear ink as a finish coat. In all other respects, the print modules 880-899 are substantially identical. The media web travels through the media path P guided by rollers 815 and 816, pre-heater roller 818, apex roller 820, and leveler roller 822. A heated plate 819 is provided along the path adjacent roller 815. In FIG. 6, the apex roller 820 is an “idler” roller, meaning that the roller rotates in response to engaging the moving media web 814, but is otherwise uncoupled from any motors or other drive mechanisms in the printing system 800. The pre-heater roller 818, apex roller 820, and leveler roller 822 are each examples of a capstan roller that engages the media web 814 on a portion of its surface. A brush cleaner 824 and a contact roller 826 are located at one end 834 of the media path P. A heater 830 and a spreader 832 are located at the opposite end 836 of the media path P.
Operation and control of the various subsystems, components and functions of printing system 800 are performed with the aid of a controller 828 and memory 829. In particular, controller 828 monitors the velocity and tension of the media web 814 and determines timing of ink drop ejection from the print modules 880-899. The controller 828 can be implemented with general or specialized programmable processors that execute programmed instructions. Controller 828 is operatively connected to memory 829 to enable the controller 828 to read instructions and to read and write data required to perform the programmed functions in memory 829. Memory 829 can also hold one or more values that identify tension levels for operating the printing system with at least one type of print medium used for the media web 814. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in VLSI circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits.
As illustrated in FIG. 8, each of the print modules 880-899 includes an array of printheads that are arranged across the width of both the first section of web media and second section of web media. Ink ejectors in each printhead in the array of printheads are configured to eject ink drops onto predetermined locations of both the first and second sections of media web 814. To provide ink for the printheads in the print modules to eject onto the continuous web 814, a solid ink delivery system receives phase change ink in solid form, such as pellets or ink sticks, and then transports the solid ink to a melting assembly where the solid phase change ink is heated to a temperature sufficient to melt the solid phase change ink. The melted phase change ink is then delivered to a reservoir and, subsequently, to the printheads in a printhead module for jetting onto a surface of web 814. Once the solid ink is melted, the ink is maintained at a temperature that preserves the liquid state of the ink to enable ejection of the ink by the inkjet ejectors in the printheads of modules 880-899, while maintaining sufficient tackiness to enable the ink to adhere to the surface of the web 814. In printers that use solid ink to produce images, melting the ink in a manner that produces liquid ink more quickly and energy efficiently is a desirable goal.